In recent years, telecommunications standards called third generation are adopted as IMT-2000 by the International Telecommunications Union (ITU) for high-speed CDMA (Code Division Multiple Access: code division multiple access) mobile telecommunications methods. For W-CDMA (FDD: Frequency Division Duplex), commercial services were started in Japan in 2001.
W-CDMA systems are originally aimed at providing a maximum transmission rate of about 2 Mbps (Mega bit per sec) per mobile station. For W-CDMA systems, the standardization organization 3GPP (3rd Generation Partnership) determined the first specifications to summarize them as the release 1999th edition (Version name: 3.x.x) in 1999.
Various written standards of the above-mentioned release (including the subsequent releases) are disclosed on the Internet, as follows, and the contents of the various written standards have been updated. Currently, release 4 and release 5 are specified as other new versions of the release 1999th edition, and release 6 is being created.
URL: http://www.3gpp.org/ftp/Specs/archive/
In the above-mentioned written standards, it is specified that “In transmission of data from a mobile station to a base station, even when burst (Burst) transmission, such as transmission of packet data, is carried out, a radio resource is always secured, as a dedicated channel (DCH: Delicated CHannel), for each mobile station.” For this reason, from the viewpoint of effective use of radio resources, useless securing of radio resources occurs.
Furthermore, since transmission of data from a mobile station to a base station is subject to autonomous transmission control (Autonomous Transmission) by the mobile station, transmission timing of each mobile station is arbitrary (random). In a CDMA communication system, since all transmission from other mobile stations serves as a source of interference, the amount of interference noises and the amount of change in the interference noise amount at the time when the base station receives data from the station can only be statistically expected.
For this reason, in the management of radio resources for the communication system, it is necessary to reduce the throughput (i.e., the maximum transmission rate of each mobile station) assuming a case where the amount of change is large, and to secure a radio resource which provides an interference margin of the base station.
Actually, control of assignment of radio resources for mobile station transmission, which is specified in the standard of W-CDMA systems, is not carried out by the base station, but is carried out by a base station controller (RNC: Radio Network Controller) which organizes base stations.
Since the control of assignment of radio resources which the base station controller carries out for each mobile station, and exchange of setup information between the base station controller and each mobile station need a relatively long processing time (of the order of several 100 msec), the base station controller cannot carry out the control of assignment of radio resources at a high speed while monitoring changes in the radio propagation environment and the transmission status of other mobile stations (e.g., the amount of interference from other mobile stations).
Then, there has been provided a method of improving the precision of the control of assignment of radio resources, which is associated with transmission of data from mobile stations, by additionally providing a function of assigning radio resources to the base station on the basis of the specifications of the above-mentioned written standard.
In FIG. 1 of R1-030067 (“AH64: Reducing control channel overhead for Enhanced Uplink”, which is referred to as nonpatent reference 1 from here on), which is a document newly proposed as uplink performance enhancement/expansion (E-DCH: Enhancement of Dedicated CHannel), an on-demand channel assignment method for uplinks is disclosed.
This document is published on the Internet as follows.
URL:http://www.3gpp.org/ftp/tsg_ran/WG1_RL1/TSGR1—30/Docs/Zips/R1-030067.zip>[retrieved on Jan. 7, 2004]
In FIG. 1 of the above-mentioned nonpatent reference, a mobile station (UE: User Equipment) having packets to be transmitted transmits a request for permission to transmit packet data to a base station (Node-B) by using a channel for transmission request (USICCH: Uplink Scheduling Information Control Channel) including amount-of-data information about yet-to-be-transmitted packet data (Queue size).
When receiving the request for permission to transmit packet data from the mobile station, the base station transmits a result (i.e., scheduling result) of the assignment of radio resources, which indicating the assignment of transmission timing to the mobile station and so on, by using a downlink channel for assignment (DSACCH: Downlink Scheduling Assignment Control Channel).
When receiving the scheduling result from the base station, the mobile station sends out packet data onto a channel for data transmission (EUDCH: Enhanced Uplink Dedicated Transport Channel) to transmit them to the base station.
In this case, the mobile station separately transmits information, including a modulation method at the time of the transmission of packet data to the base station, to the base station by using a type-of-modulation information channel (UTCCH: Uplink TFRI Control Channel).
When receiving the packet data from the mobile station, the base station sends out information about a result of determination of the reception of the packet data (i.e., so-called ACK/NACK) onto a channel for notification (DANCCH: Downlink Ack/Nack Control Channel) to transmit it to the mobile station.
Although it can be assumed that these channels are an extension of conventional standard channels, or new channels which are introduced into the system, the details of the channels have not proposed yet.
A technology for notifying amount-of-data information from a mobile station to a base station is also disclosed by patent reference 1 (JP,2003-46482,A).
In the conventional standards of W-CDMA systems, although information about the amount of yet-to-be-transmitted data transmitted from a mobile station is temporarily received by a base station, the information about the amount of yet-to-be-transmitted data passes through the base station and is then transmitted to a base station controller juts as it is. For this reason, the base station cannot grasp the contents of the information about the amount of yet-to-be-transmitted data. Therefore, the base station cannot carry out the control of radio resources, unlike that as disclosed in above-mentioned nonpatent reference 1.
Even when it is possible to provide a means for temporarily transmitting information which the base station controller has acquired to the base station, the base station cannot carry out the control of radio resources at a high speed since the period of transmission of the amount information about yet-to-be-transmitted data from the mobile station to the base station controller is a long one (e.g., 250 ms, 500 ms, . . . , or 6000 ms).
A proposal about transmission timing of a notification of amount-of-data information about yet-to-be-transmitted data, which relates to the on-demand channel assignment method disclosed in above-mentioned nonpatent reference 1, is disclosed in R1-031056 (“Uplink signalling of scheduling information”, which is referred to as nonpatent reference 2 from here on). In this proposal, various types of transmission methods, such as a periodic transmission method, are provided.
This document is published on the Internet as follows.
URL:http://www.3gpp.org/ftp/tsg_ran/WG1_RL1/TSGR1—34/Docs/Zips/R1-030056.zip>[retrieved on Jan. 7, 2004]
However, in W-CDMA systems, since one mobile station can carry out two or more communication services simultaneously, data having different priorities and demands for different delay times (i.e., different levels of so-called QoS: Quality of Service) coexist in the mobile station. Therefore, in the above-mentioned references, since such a case is not taken into consideration, it can be assumed that information about the total amount of data is only notified to the base station.
A problem with related art communication systems constructed as mentioned above is that even if information about the total amount of data is notified to the base station, the base station cannot grasp the amount of data on a communication-service-by-communication-service or transmit-channel-by-transmit-channel, and therefore cannot properly control the transmission timing of data on a communication-service-by-communication-service or transmit-channel-by-transmit-channel.
The present invention is made in order to solve the above-mentioned problem, and it is therefore an object of the present invention to provide a base station, a communication system, a transmission-control-information notification method, and a wireless communication method which can properly control the transmission timing of data on a communication-service-by-communication-service or transmit-channel-by-transmit-channel.
It is another object of the present invention to provide a mobile station and an amount-of-data information transmission method which enable a base station to properly control the transmission timing of data on a communication-service-by-communication-service or transmit-channel-by-transmit-channel.